Speaking of doing well, how much you think XV actually needs to sell to be a sucess in S.E eyes?
Well, I might put the total figure at around six million. I believe they estimated that XIII would sell around five million worldwide, and it cleared that by over a million units. It would be silly to overestimate sales expectations, even with the expected entry in a major brand. Something I do think is that first week sales will be higher in the West than in Japan: not only will it be going against other titles such as Persona and Dragon Quest (both firm JP favorites), but action RPGs seem to be less popular than they are in the West. Final Fantasy isn't the giant it used to be, so they can't expect the massive targets of their earlier entries.
Personally, I'd put their Japanese figures at maybe 500,000 to one million, with figures going into the millions in North America and Europe. It will probably be an unknown quantity in South America, so who knows whether it will see commercial success there.
Something else to consider is the budget: they've said it was being kept under control, but we still don't know how much is being spent on it, and that's before any marketing costs. Something I do think is that they're trying to avoid the spiraling costs of the XIII games by taming and modernizing their development methods. That's something Tabata would probably be good at, as he's spent the majority of his career at Square Enix working with mobile and portable titles, which by definition have smaller budgets than home console titles.
Ideally, it will be a massive success and get into the double figures due to it being for next-gen consoles, a long-awaited entry in the series and more accessible to gamers than many previous titles. A bit like how FE Awakening catapulted Fire Emblem sales for an individual game into the millions when it had hung around in the hundred thousands for all its life.